what I found to help me was to do all the same longs on all the blocks the same day, ie: round 4 blue log, do all round 4 logs, as I found one day I was doing a scant 1/4" and the next day a 1/4, I do strip piecing and it works for me, I love log cabin quilts, some of mine":
http://www.quiltingboard.com/picture...ns-t60783.html
I also make several blocks more than I need, My planed overs: so if one block is a tad too small or too big, I use it in another project, bed runner, nap quilt, wall hanging, or hot pads. hope this helps